Sound processing device

Abstract

The sound processing apparatus according to the present disclosure has a first sound processing unit, a second sound processing unit, and one or more microphones. The second sound processing unit can be connected between some or all of the microphones and the first sound processing unit. The second sound processing unit has an operational amplifier, an output terminal, an attenuator, and a transistor. The output terminal can be connected to the first sound processing unit. The attenuator is electrically connected between an output node of the operational amplifier and the output terminal.

Description

Technical Field

[0001] This disclosure relates to an audio processing device. Background Technology

[0002] The audio processing unit installed in the vehicle uses a microphone for signal processing such as hands-free calling and voice recognition, or for noise control such as noise suppression and active noise control (ANC) in the vehicle interior. Summary of the Invention

[0003] In audio processing devices, microphones for signal processing and microphones for noise control are mostly configured as separate modules. To improve the performance of signal processing and noise control, the number of microphones is increasing, and the centralized wiring for subsequent audio processing units may also hinder the routing of wire harnesses.

[0004] This disclosure provides an audio processing apparatus capable of reducing the number of microphones.

[0005] The effects of the invention

[0006] According to the audio processing apparatus disclosed herein, the number of microphones can be reduced. Attached Figure Description

[0007] Figure 1 This is a circuit diagram showing the structure of the audio processing device involved in the embodiment.

[0008] Figure 2 This is a circuit diagram illustrating the structure of the audio processing device involved in the first variation of the embodiment.

[0009] Figure 3 This is a circuit diagram illustrating the structure of the audio processing device involved in the second variation of the embodiment.

[0010] Figure 4 This is a circuit diagram showing the structure of an audio processing device when the microphone for sound recognition and the microphone for noise control are different modules. Detailed Implementation

[0011] Hereinafter, embodiments of the audio processing apparatus involved in this disclosure will be described with reference to the accompanying drawings.

[0012] (Implementation Method)

[0013] The audio processing device described in this embodiment is installed inside a vehicle and includes a microphone. The microphone inside the vehicle is used for various purposes, including hands-free calling, voice recognition, noise suppression in the vehicle interior, and active noise control (ANC). The audio processing device uses the microphone to perform signal processing for hands-free calling and voice recognition, or noise control such as noise suppression in the vehicle interior and active noise control (ANC).

[0014] In audio processing devices, microphones for signal processing and microphones for noise control are mostly constructed as separate modules. To improve the performance of both signal processing and noise control, the number of microphones is trending upwards.

[0015] For example, Figure 4 The audio processing device 1000 shown includes microphones 11a, 11b, 11c, microphones 21a, 21b, 21d, an ANC unit 1002, and a signal processing unit 1003. Figure 4 This is a circuit diagram showing the structure of an audio processing device 1000 when the microphone for signal processing and the microphone for noise control are different modules.

[0016] Microphones 11a, 11b, and 11c are microphone modules for ANC (Automatic Numerical Control) and possess the characteristics required by ANC unit 1002. Microphones 21a, 21b, and 21d are microphone modules for signal processing and possess the characteristics required by signal processing unit 1003. Microphones 11a, 11b, 11c and 21a, 21b, and 21d are all types of microphones that are powered externally, such as condenser microphones.

[0017] The power supply to microphones 11a, 11b, and 11c is provided via phantom power. The signal lines La1, La2, Lb1, Lb2, Lc1, and Lc2 connecting microphones 11a, 11b, and 11c to the ANC unit 1002 are shared in both power supply and microphone output.

[0018] The power supply to microphones 21a, 21b, and 21d is provided via phantom power. The signal lines LLa1, LLa2, LLa1, LLa2, LLa1, LLa2, LLa1, LLa2, LLa1, and LLa2 connecting microphones 21a, 21b, and 21d to the signal processing unit 1003 are shared in both power supply and microphone output.

[0019] The ANC unit 1002 has input terminals 2a1, 2a2, 2b1, 2b2, 2c1, 2c2 and phantom power circuits 212a, 212b, 212c. The phantom power circuits 212a, 212b, 212c each have a power supply voltage Vcc and resistors 201a, 201b, 201c. One end of resistors 201a, 201b, 201c is connected to the power supply voltage Vcc, and the other end is connected to microphones 11a, 11b, 11c via input terminals 2a1, 2b1, 2c1 and signal lines La1, Lb1, Lc1, respectively. Thus, the phantom power circuits 212a, 212b, 212c supply power voltage to microphones 11a, 11b, 11c. Additionally, microphones 11a, 11b, 11c supply audio signals to the ANC unit 1002.

[0020] The signal processing unit 1003 has input terminals 1003a1, 1003a2, 1003b1, 1003b2, 1003d1, and 1003d2, and phantom power circuits 312a, 312b, and 312d. The phantom power circuits 312a, 312b, and 312d each have a power supply voltage Vcc and resistors 301a, 301b, and 301d. One end of each resistor 301a, 301b, and 301d is connected to the power supply voltage Vcc, and the other end is connected to microphones 21a, 21b, and 21d via the input terminals 1003a1, 1003b1, and 1003d1 and signal lines LLa1, LLLb1, and LLLd1, respectively. Thus, the phantom power circuits 312a, 312b, and 312d supply power voltage to microphones 21a, 21b, and 21d, respectively. In addition, microphones 21a, 21b, and 21d supply sound signals to the signal processing unit 1003.

[0021] Additionally, the ANC unit 1002 includes disconnection detection circuits 213a, 213b, and 213c, amplifier circuits 214a, 214b, and 214c, and sound processing units 211a, 211b, and 211c. The disconnection detection circuits 213a, 213b, and 213c each have diodes 202a, 202b, and 202c, and resistors 203a, 203b, and 203c. The anodes of diodes 202a, 202b, and 202c are connected to the node between the other end of resistors 201a, 201b, and 201c and signal lines La1, Lb1, and Lc1, respectively, while the cathodes are connected to one end of resistors 203a, 203b, and 203c. The other ends of resistors 203a, 203b, and 203c are connected to ground potential. The cathode voltages of diodes 202a, 202b, and 202c vary depending on the connection status (normal, open, short circuit) of microphones 11a, 11b, and 11c via signal lines La1, Lb1, and Lc1. That is, the connection status (normal, open, short circuit) of microphones 11a, 11b, and 11c can be detected by monitoring the cathode voltages of diodes 202a, 202b, and 202c.

[0022] Amplifier circuits 214a, 214b, and 214c respectively include capacitors 204a, 204b, and 204c, capacitors 205a, 205b, and 205c, operational amplifiers 206a, 206b, and 206c, and capacitors 208a, 208b, and 208c. Operational amplifiers 206a, 206b, and 206c operate by receiving power supply voltage Vcc through a power supply node. Operational amplifiers 206a, 206b, and 206c amplify the audio signals transmitted from signal lines La1, Lb1, and Lc1 via capacitors 204a, 204b, and 204c, and capacitors 205a, 205b, and 205c, respectively, to a specified level. Operational amplifiers 206a, 206b, and 206c supply the amplified signals to sound processing units 211a, 211b, and 211c via capacitors 208a, 208b, and 208c, respectively. Sound processing units 211a, 211b, and 211c extract noise components from the supplied signal and generate noise cancellation signals with opposite phase to the noise components. Sound processing units 211a, 211b, and 211c output noise cancellation tones corresponding to the noise cancellation signals from a loudspeaker (not shown).

[0023] The signal processing unit 1003 includes disconnection detection circuits 313a, 313b, and 313d, amplifier circuits 314a, 314b, and 314d, and sound processing units 311a, 311b, and 311d. The disconnection detection circuits 313a, 313b, and 313d each have diodes 302a, 302b, and 302d, and resistors 303a, 303b, and 303d. The anodes of diodes 302a, 302b, and 302d are connected to the node between the other end of resistors 301a, 301b, and 301d and signal lines LLa1, LLb1, and LLd1, respectively, while the cathodes are connected to one end of resistors 303a, 303b, and 303d. The other ends of resistors 303a, 303b, and 303d are connected to ground potential. The cathode voltages of diodes 302a, 302b, and 302d vary according to the connection status (normal, open, short) of microphones 21a, 21b, and 21d via signal lines LLa1, LLb1, and LLd1. That is, the connection status (normal, open, short) of microphones 21a, 21b, and 21d can be detected by monitoring the cathode voltages of diodes 302a, 302b, and 302d.

[0024] Amplifier circuits 314a, 314b, and 314d include capacitors 304a, 304b, and 304d, capacitors 305a, 305b, and 305d, operational amplifiers 306a, 306b, and 306d, and capacitors 308a, 308b, and 308d, respectively. Operational amplifiers 306a, 306b, and 306d operate by receiving power supply voltage Vcc through a power supply node. Operational amplifiers 306a, 306b, and 306d amplify the audio signals transmitted from signal lines LLa1, LLb1, and LLd1 via capacitors 304a, 304b, and 304d, and capacitors 305a, 305b, and 305d, respectively, to a specified level. Operational amplifiers 306a, 306b, and 306d supply the amplified signals to sound processing units 311a, 311b, and 311d via capacitors 308a, 308b, and 308d, respectively. Sound processing units 311a, 311b, and 311d extract signal components from the supplied signal and generate output sound signals. Sound processing units 311a, 311b, and 311d then output the corresponding sound from a speaker (not shown). Furthermore, sound processing units 311a, 311b, and 311d generate operation commands corresponding to the output sound signals and send them to the device. Thus, the device can be operated based on the input sound.

[0025] exist Figure 4The following scenario illustrates the following: Three microphones (11a, 11b, and 11c) are needed for ANC (Automatic Control), and three microphones (21a, 21b, and 21d) are needed for signal processing, totaling six microphones. Inside the vehicle, the ANC unit 1002 is positioned between microphones 11a, 11b, 11c and 21a, 21b, 21d, and the signal processing unit 1003. Therefore, the three microphones 11a, 11b, 11c are connected to the ANC unit 1002 via six short signal lines La1, La2, Lb1, Lb2, Lc1, and Lc2. The three microphones 21a, 21b, 21d are connected to the signal processing unit 1003 via six long signal lines LLa1, LLa2, LLb1, LLb2, LLd1, and LLd2.

[0026] For example, there are cases where microphones 11a, 11b, and 11c are required to have flat levels and phases in the low-frequency region, without concern for their characteristics in the high-frequency region. On the other hand, for microphones 21a, 21b, and 21d, in most cases, the flatness of levels and phases in the low-frequency region required for microphones 11a, 11b, and 11c is not a concern; instead, the requirements for their characteristics in the high-frequency region, as exemplified by international standards such as ITU-T, are becoming increasingly stringent year by year.

[0027] When the number of microphones is increased for the purpose of improving performance, the number of signal lines connecting the ANC unit 1002 and the signal processing unit 1003 also increases, making it unavoidable to concentrate the wiring. This concentration of wiring, including long signal lines for the subsequent signal processing unit, may also hinder the routing of the wire harness.

[0028] Therefore, in this embodiment, the audio processing device is configured such that the output level of the microphone and the output level of the ANC unit 2 are equal to each other, thereby enabling the subordinate connection of the ANC unit and the signal processing unit, realizing the reduction of the number of microphones, the reduction of wiring concentration for the signal processing unit, and the detection of disconnection of each microphone / unit.

[0029] Specifically, the audio processing device 100 is capable of... Figure 1 It is constructed as shown. Figure 1 This is a diagram showing the structure of the audio processing device 100. Below, it will be compared with... Figure 4 The different parts of the audio processing device 1000 shown will be explained in detail.

[0030] The audio processing device 100 includes microphones 1a, 1b, 1c, 1d and an ANC unit (second audio processing unit) 2, replacing microphones 11a, 11b, 11c, microphones 21a, 21b, 21d and ANC unit 1002 (see reference). Figure 4 The ANC unit 2 is configured between microphones 1a, 1b, 1c, 1d and the signal processing unit (first sound processing unit) 1003.

[0031] Microphones 1a, 1b, 1c, and 1d possess characteristics required by both the ANC unit 2 and the signal processing unit 1003. Microphones 1a, 1b, 1c, and 1d are microphones that are externally powered for operation, such as condenser microphones. Microphones 1a, 1b, 1c, and 1d share signal lines La1, La2, Lb1, Lb2, Lc1, Lc2, LLd1, and LLd2 for both power supply and microphone output.

[0032] exist Figure 1 The following structure is illustrated: microphones 1a and 1b are used for ANC and signal processing, microphone 1c is used for ANC, and microphone 1d is used for signal processing. Microphones 1a and 1b are subordinately connected to ANC unit 2 and signal processing unit 1003 on their output sides. Therefore, three microphones 1a, 1b, and 1c are used for ANC, and three microphones 1a, 1b, and 1d are used for signal processing, for a total of four microphones. That is, in... Figure 1 In the structure, with Figure 4 Compared to the previous structure, this allows for a reduction in the number of microphones.

[0033] In addition, Figure 1 In the structure, microphones 1a and 1b are connected to ANC unit 2 via four short signal lines La1, La2, Lb1, and Lb2, and ANC unit 2 is connected to signal processing unit 1003 via four short signal lines La11, La12, Lb11, and Lb12. When viewed from signal processing unit 1003, four of the six signal lines are replaced from long signal lines (LLa1, LLa2, Lb1, Lb2) to short signal lines (La11, La12, Lb11, Lb12). This reduces the number of bends in the wiring to signal processing unit 1003. That is, in Figure 1 In the structure, with Figure 4 Compared to the previous structure, this reduces the wiring concentration for the signal processing unit 1003.

[0034] ANC unit 2 includes phantom power circuits 212a, 212b, 212c, disconnection detection circuits 213a, 213b, 213c, amplifier circuits 214a, 214b, 214c, and sound processing units 211a, 211b, 211c (see reference). Figure 4In addition to the above, it also includes adjustment circuits 215a, 215b, and 215c, and output terminals 2a11, 2a12, 2b11, 2b12, 2c11, and 2c12. Adjustment circuits 215a, 215b, and 215c adjust the output level of ANC unit 2 to be equal to the output levels of microphones 1a, 1b, and 1c. Adjustment circuits 215a, 215b, and 215c are connected to signal processing unit 1003 via output terminals 2a11, 2a12, 2b11, 2b12, 2c11, and 2c12, and signal lines La11, La12, Lb11, Lb12, Lc11, and Lc12, respectively.

[0035] Adjustment circuits 215a, 215b, and 215c each include capacitors 207a, 207b, and 207c; attenuators (ATTs) 209a, 209b, and 209c; and transistors 210a, 210b, and 210c. One end of capacitors 207a, 207b, and 207c is connected to the output node of operational amplifiers 206a, 206b, and 206c, respectively, and the other end is connected to attenuators 209a, 209b, and 209c, respectively. One end of attenuators 209a, 209b, and 209c is connected to capacitors 207a, 207b, and 207c, and the other end is connected to transistors 210a, 210b, and 210c.

[0036] Transistors 210a, 210b, and 210c are, for example, PNP bipolar transistors, connected to output terminals 2a11, 2b11, and 2c11 with open emitters. That is, the bases of transistors 210a, 210b, and 210c are connected to attenuators 209a, 209b, and 209c; their emitters are connected to output terminals 2a11, 2b11, and 2c11; and their collectors are connected to ground and output terminals 2a12, 2b12, and 2c12. The emitters of transistors 210a and 210b are connected to signal processing unit 1003 via output terminals 2a11 and 2b11 and signal lines La11 and Lb11, and their collectors are connected to signal processing unit 1003 via output terminals 2a12 and 2b12 and signal lines La12 and Lb12. The collector and emitter of transistor 210c are not connected to signal processing unit 1003.

[0037] At this time, attenuators 209a, 209b, and 209c have attenuation amounts corresponding to the amplification amounts of the signals amplified by operational amplifiers 206a, 206b, and 206c. For example, attenuators 209a, 209b, and 209c have attenuation amounts that eliminate the amplification amounts of the signals amplified by operational amplifiers 206a, 206b, and 206c. Therefore, the output levels of the signals transmitted through attenuators 209a, 209b, and 209c to output terminals 2a11, 2a12, 2b11, 2b12, 2c11, and 2c12 via transistors 210a, 210b, and 210c can be made close to the output levels of microphones 1a, 1b, and 1c. As a result, the output levels of microphones 1a, 1b, and 1c can be made equal to the output levels of ANC unit 2.

[0038] In addition, attenuators 209a, 209b, and 209c are configured such that their input impedances are equal to those of the sound processing units 211a, 211b, and 211c.

[0039] For example, the output levels of microphones 1a, 1b, and 1c are assumed to be -20dBV. Operational amplifiers 206a, 206b, and 206c amplify the signal to a level suitable for consumption within the ANC unit 2. The outputs of operational amplifiers 206a, 206b, and 206c are branched into two branches. One output is input to the sound processing units 211a to 211c with a specified input impedance, and the other output is input to the attenuators 209a to 209c with a specified input impedance.

[0040] At this time, attenuators 209a, 209b, and 209c can be configured by connecting multiple resistors in a Π-type or T-type configuration. In the Π-type or T-type configuration, the input impedance of attenuators 209a, 209b, and 209c can be adjusted to be equal to the input impedance of sound processing units 211a, 211b, and 211c. Therefore, the output level of operational amplifiers 206a, 206b, and 206c can be the same whether the signal processing unit 1003 is connected after transistors 210a to 210c or not.

[0041] Furthermore, the attenuation of attenuators 209a, 209b, and 209c can be adjusted to make the output levels of microphones 1a, 1b, and 1c equal to the output level of ANC unit 2. For example, in the Π-type or T-type structure of attenuators 209a, 209b, and 209c, the output levels of transistors 210a, 210b, and 210c can be made equal to the output levels of microphones 1a, 1b, and 1c by adjusting the resistance values ​​of each resistor. For example, the attenuation of attenuators 209a to 209c can be set to make the output level of transistors 210a to 210c -20dBV.

[0042] Furthermore, since the output levels of transistors 210a, 210b, and 210c can be made equal to the output levels of microphones 1a, 1b, and 1c, when observing ANC unit 2 from signal processing unit 1003, the connected signals can be made equal in both cases where microphones are connected and where microphones are connected via ANC unit 2. Therefore, ANC unit 2 and signal processing unit 1003 can operate stably in both cases where the output sides of microphones 1a, 1b, 1c, and 1d are subordinately connected to ANC unit 2 and signal processing unit 1003 and directly connected to signal processing unit 1003.

[0043] For example, since the operating points of microphones 1a, 1b, 1c, and 1d can be kept constant, the connection status (normal, open circuit, short circuit) of microphones 1a, 1b, and 1c can be appropriately detected by monitoring the cathode voltages of diodes 202a, 202b, and 202c in the disconnection detection circuits 213a, 213b, and 213c. Similarly, the connection status (normal, open circuit, short circuit) of ANC unit 2 can be appropriately detected by monitoring the cathode voltages of diodes 302a, 302b, and 302d in the disconnection detection circuits 313a, 313b, and 313d.

[0044] As described above, in this embodiment, the audio processing device 100 is configured such that the output levels of microphones 1a-1d and the output level of ANC unit 2 are equal. Therefore, ANC unit 2 and signal processing unit 1003 can be subordinately connected to the output side of microphones 1a-1d, thus reducing the number of microphones and consequently reducing wiring concentration for signal processing unit 1003. Furthermore, disconnection detection can be performed on microphones and ANC unit 2 via independent channels.

[0045] In addition, when it is desired to enhance noise control, the ANC unit 2 can be configured to be subordinately connected in multiple levels between the microphone 1 and the signal processing unit 1003.

[0046] In addition, operational amplifiers 206a, 206b, 206c, 306a, 306b, and 306d can also be implemented by replacing the differential input structure with a single-ended input structure.

[0047] Furthermore, if microphone 1c can be used instead of microphone 1d, the audio processing device 200 can also be as follows: Figure 2 As shown, the ANC unit 2 and the signal processing unit 1003 are subordinately connected on the output side of the microphone 1c. This allows for a further reduction in the number of microphones and a further reduction in the wiring density of the signal processing unit 1003. For example, it allows for... Figure 1 The four microphones shown (1a-1d) are reduced to... Figure 2 The three microphones shown are 1a to 1c, and are capable of... Figure 1 The long signal lines LLd1 and LLd2 shown are replaced with Figure 2 The short signal lines Lc11 and Lc12 shown are used to further reduce the routing bends for the signal processing unit 1003.

[0048] In this embodiment and its variations, an ANC unit 2 is illustrated in the pre-amplifier configuration of the signal processing unit 1003, but the audio processing device 300 may also be configured as follows. Figure 3 The signal processing unit 3 is configured in front of the ANC unit 1002 as shown. For example, Figure 3 The audio processing device 300 shown includes microphones 1a, 1b, 1c, 1d and a signal processing unit (second audio processing unit) 3, replacing microphones 11a, 11b, 11c, microphones 21a, 21b, 21d and signal processing unit 1003 (see reference). Figure 4 The signal processing unit 3 is configured between microphones 1a, 1b, 1c, and 1d and the ANC unit (first sound processing unit) 1002. The ANC unit 1002 and... Figure 4 The ANC unit 1002 shown is the same. Signal processing unit 3 is an improvement upon signal processing unit 1003 (see reference 1003). Figure 4 This is obtained by applying the same changes to the ANC unit 1002 as those applied to obtain the ANC unit 2 in the embodiment. The signal processing unit 3 includes phantom power circuits 312a, 312b, 312c, disconnection detection circuits 313a, 313b, 313c, amplification circuits 314a, 314b, 314c, and sound processing units 311a, 311b, 311c (see reference). Figure 4In addition to the signal processing unit 3, it also includes adjustment circuits 315a, 315b, and 315c, and output terminals 3a11, 3a12, 3b11, 3b12, 3c11, and 3c12. Adjustment circuits 315a, 315b, and 315c adjust the signal to make the output level of the signal processing unit 3 equal to the output levels of the microphones 1a, 1b, and 1c. Adjustment circuits 315a, 315b, and 315c each include capacitors 307a, 307b, and 307c, attenuators (ATTs) 309a, 309b, and 309c, and transistors 310a, 310b, and 310c. Details regarding each structure are the same as in the embodiment, therefore, descriptions are omitted.

[0049] Several embodiments of the present invention have been described. These embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention as well as in the invention as described in the claims and its equivalents.

[0050] Explanation of reference numerals in the attached figures

[0051] 1a, 1b, 1c, 1d, 11a, 11b, 11c, 21a, 21b, 21d: Microphones; 2, 1002: ANC unit; 2a1, 2a2, 2b1, 2b2, 2c1, 2c2: Input terminals; 2a11, 2a12, 2b11, 2b12, 2c11, 2c12: Output terminals; 100, 200, 300, 1000: Audio processing unit; 206a, 206b, 206c, 3 06a, 306b, 306d: Operational amplifiers; 209a, 209b, 209c: Attenuators; 211a, 211b, 211c, 311a, 311b, 311d: Sound processing unit; 312a, 312b, 312d: Phantom power circuit; 3, 1003: Signal processing unit; 1003a1, 1003a2, 1003b1, 1003b2, 1003d1, 1003d2: Input terminals.

Claims

1. An audio processing device, comprising: First microphone; Second microphone; Third microphone; Fourth microphone; A first sound processing unit is capable of being connected to the fourth microphone; as well as The second sound processing unit is capable of connecting to the first microphone, the second microphone, and the third microphone. The first sound processing unit has: First operational amplifier; Second operational amplifier; Third operational amplifier; The first input terminal is capable of being connected to the second sound processing unit; A second input terminal, which can be connected to the second sound processing unit; and The third input terminal can be connected to the fourth microphone. The second sound processing unit has: A fourth operational amplifier is electrically connected to the first microphone; The fifth operational amplifier is electrically connected to the second microphone; A sixth operational amplifier, which is electrically connected to the third microphone; The first sound processing unit is electrically connected to the output node of the fourth operational amplifier; The second sound processing unit is electrically connected to the output node of the fifth operational amplifier; The third sound processing unit is electrically connected to the output node of the sixth operational amplifier; A first output terminal is capable of being connected to the first input terminal of the first sound processing unit; The second output terminal can be connected to the second input terminal of the first sound processing unit; Third output terminal; The first attenuator is electrically connected between the output node of the fourth operational amplifier and the first output terminal; A second attenuator is electrically connected between the output node of the fifth operational amplifier and the second output terminal; and The third attenuator is electrically connected between the output node of the sixth operational amplifier and the third output terminal. The first attenuator of the second sound processing unit has a first attenuation corresponding to a first amplification amount of the signal amplified by the fourth operational amplifier of the second sound processing unit. The second attenuator of the second sound processing unit has a second attenuation corresponding to the second amplification amount of the signal amplified by the fifth operational amplifier of the second sound processing unit. The third attenuator of the second sound processing unit has a third attenuation corresponding to the third amplification amount of the signal amplified by the sixth operational amplifier of the second sound processing unit. The first amplification is eliminated by the first attenuation. The second amplification is eliminated by the second attenuation. The third amplification is eliminated by the third attenuation. The input impedance of the first attenuator is equal to the input impedance of the first sound processing unit, the input impedance of the second attenuator is equal to the input impedance of the second sound processing unit, and the input impedance of the third attenuator is equal to the input impedance of the third sound processing unit.

2. The audio processing device according to claim 1, wherein, The second sound processing unit also has: The first transistor is electrically connected between the first attenuator and the first output terminal; The second transistor is electrically connected between the second attenuator and the second output terminal; as well as The third transistor is electrically connected between the third attenuator and the third output terminal.

3. The sound processing apparatus according to claim 1 or 2, wherein, The first microphone, the second microphone, the third microphone, and the fourth microphone are each condenser microphones.

4. The audio processing apparatus according to claim 2, wherein, The first transistor is connected to the first output terminal with its emitter open circuit. The second transistor is connected to the second output terminal with its emitter open. The third transistor is connected to the third output terminal with its emitter open.

5. The audio processing apparatus according to claim 4, wherein, The base of the first transistor is electrically connected to the first attenuator, the emitter of the first transistor is electrically connected to the first output terminal, and the collector of the first transistor is electrically connected to ground. The base of the second transistor is electrically connected to the second attenuator, the emitter of the second transistor is electrically connected to the second output terminal, and the collector of the second transistor is electrically connected to ground. The base of the third transistor is electrically connected to the third attenuator, the emitter of the third transistor is electrically connected to the third output terminal, and the collector of the third transistor is electrically connected to ground potential.

6. An audio processing device, comprising: First microphone; Second microphone; Third microphone; First sound processing unit; and The second sound processing unit is capable of connecting to the first microphone, the second microphone, and the third microphone. in, The first sound processing unit has: First operational amplifier; Second operational amplifier; Third operational amplifier; The first input terminal is capable of being connected to the second sound processing unit; The second input terminal is capable of being connected to the second sound processing unit; as well as The third input terminal can be connected to the second sound processing unit. The second sound processing unit has: A fourth operational amplifier is electrically connected to the first microphone; The fifth operational amplifier is electrically connected to the second microphone; A sixth operational amplifier, which is electrically connected to the third microphone; The first sound processing unit is electrically connected to the output node of the fourth operational amplifier; The second sound processing unit is electrically connected to the output node of the fifth operational amplifier; The third sound processing unit is electrically connected to the output node of the sixth operational amplifier; A first output terminal is capable of being connected to the first input terminal of the first sound processing unit; The second output terminal can be connected to the second input terminal of the first sound processing unit; The third output terminal is capable of being connected to the third input terminal of the first sound processing unit; The first attenuator is electrically connected between the output node of the fourth operational amplifier and the first output terminal; The second attenuator is electrically connected between the output node of the fifth operational amplifier and the second output terminal; as well as The third attenuator is electrically connected between the output node of the sixth operational amplifier and the third output terminal. The first attenuator of the second sound processing unit has a first attenuation corresponding to a first amplification amount of the signal amplified by the fourth operational amplifier of the second sound processing unit. The second attenuator of the second sound processing unit has a second attenuation corresponding to the second amplification amount of the signal amplified by the fifth operational amplifier of the second sound processing unit. The third attenuator of the second sound processing unit has a third attenuation corresponding to the third amplification amount of the signal amplified by the sixth operational amplifier of the second sound processing unit. The first amplification is eliminated by the first attenuation. The second amplification is eliminated by the second attenuation. The third amplification is eliminated by the third attenuation. The input impedance of the first attenuator is equal to the input impedance of the first sound processing unit, the input impedance of the second attenuator is equal to the input impedance of the second sound processing unit, and the input impedance of the third attenuator is equal to the input impedance of the third sound processing unit.

7. The audio processing apparatus according to claim 6, wherein, The second sound processing unit also has: The first transistor is electrically connected between the first attenuator and the first output terminal; The second transistor is electrically connected between the second attenuator and the second output terminal; as well as The third transistor is electrically connected between the third attenuator and the third output terminal.

8. The sound processing apparatus according to claim 6 or 7, wherein, The first microphone, the second microphone, and the third microphone are each condenser microphones.

9. The audio processing apparatus according to claim 7, wherein, The first transistor is connected to the first output terminal with its emitter open circuit. The second transistor is connected to the second output terminal with its emitter open. The third transistor is connected to the third output terminal with its emitter open.

10. The audio processing apparatus according to claim 9, wherein, The base of the first transistor is electrically connected to the first attenuator, the emitter of the first transistor is electrically connected to the first output terminal, and the collector of the first transistor is electrically connected to ground. The base of the second transistor is electrically connected to the second attenuator, the emitter of the second transistor is electrically connected to the second output terminal, and the collector of the second transistor is electrically connected to ground. The base of the third transistor is electrically connected to the third attenuator, the emitter of the third transistor is electrically connected to the third output terminal, and the collector of the third transistor is electrically connected to ground potential.

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